Top view of a child with asymmetric brachydactyly type D thumb.
Classification and external resources
Side view of a child with asymmetric BDD
"Clubbed thumb" is a misnomer for stub(by) thumb, known clinically as brachydactyly type D, orBDD. BDD is a harmless genetic trait characterized by the last bone of one or both thumbs being short and round with an accompanying short and wide nail bed.
Digital clubbing, however, is a "clinical sign associated with a number of diseases."
Because of the supposed high incidence of BDD among European royalty in the past, BDD is claimed by some to be a marker of descent from European nobility.The condition is also sometimes known as potter's thumb.